1. Field of the Invention
The present invention relates to a four-cycle engine and an improvement to a lubrication structure therefor.
2. Description of Related Art
In, for example, Utility Model Laid-open Publication No. Sho. 63-22356, entitled "Two-cycle Internal Combustion Engine Vibration Control Assembly", there is disclosed in FIG. 2 a crankcase 3, a crankshaft 7 and a balancing weight 13 housed in a rotatable manner within this crankcase 3, a support shaft 23 extending out of the crankcase 3 from an end of the crankshaft 7, a gear 14 attached to the support shaft 23, a support shaft 24 extending out of the crankcase 3 from an end of the shaft for the balancing weight 13, and a gear 15 attached to the support shaft 24 and meshing with the gear 14 in such a manner as to rotate the balancing weight 13.
In the above technology, it is necessary to lubricate the meshing part of the gear 14 and the gear 15 and special apparatus is therefore necessary to spray oil on the meshing parts and to gather up the remaining oil. Therefore, costs are substantially increased.
The gear 14 and gear 15 have to be sealed from the outside due to this lubrication. Therefore the engine is increased in size, causing many disadvantages.